1. Field of the Invention
The present invention relates to a rotation transmitting device incorporating a one-way clutch that can be used as a driven pulley secured to an end of a rotating shaft of an alternator, which is, for example, an automotive generator, or as a pinion or the like secured to an end of a rotating shaft constituting a starter motor of an automotive starting device.
2. Description of the Related Art
FIG. 10 is a longitudinal sectional view showing a conventional alternator disclosed in, for example, Japanese Unexamined Patent Application Publication No. 7-139550.
Referring to FIG. 10, a rotating shaft 3 is rotatably supported by a pair of ball-and-roller bearings 4 in a housing 2. A rotor 5 and a commutator 6 are provided at a middle portion of the rotating shaft 3. A driven pulley 7 is secured to an end of the rotating shaft 3 extending out from one end (the right end in FIG. 10) of the housing 2.
When the alternator 1 configured as described above has been installed to an engine, an endless belt (not shown) is installed on the driven pulley 7. Motive power of a crankshaft of the engine is transmitted via an endless belt to the rotating shaft 3 to rotatably drive the rotating shaft, thereby generating power necessary for an automobile.
Hitherto, in general, the driven pulley 7 is simply secured to the rotating shaft 3. In recent years, however, a pulley device incorporating a one-way clutch has been proposed in, for example, Japanese Unexamined Patent Application Publication No. 56-101353, Japanese Unexamined Patent Application Publication No. 7-317807, Japanese Unexamined Patent Application Publication No. 8-61443, Japanese Unexamined Patent Application Publication No. 8-226462, Japanese Unexamined Patent Application Publication No. 11-22753, and Japanese Examined Patent Application Publication No. 7-72585. The pulley device is a rotation transmitting device with a built-in one-way clutch in which motive power is freely transmitted from an endless belt to a rotating shaft if a running speed of the endless belt is fixed or increasing, while relative rotation of the driven pulley and the rotating shaft is allowed if the running speed of the endless belt is decreasing.
FIG. 11 is a longitudinal sectional view showing an essential section of a conventional pulley device including a one-way clutch, FIG. 12 is a fragmentary sectional view taken at the line XIIxe2x80x94XII of FIG. 11, and FIG. 13 is a perspective view showing an essential section of a retaining frame employed with the conventional pulley device including the one-way clutch.
Referring to FIG. 11 through FIG. 13, the pulley device with the built-in one-way clutch has a sleeve 8, which is an inner member that can be fixedly and externally fitted to the rotating shaft 3 of the alternator 1. A driven pulley 7a, which is a cylindrical outer member, is disposed concentrically with the sleeve 8. A pair of support bearings 9 and a roller clutch 10, which is the one-way clutch, are provided between an outer peripheral surface of the sleeve 8 and an inner peripheral surface of the driven pulley 7a. 
The entire sleeve 8 is formed to be cylindrical, fixedly and externally fitted to an end of the rotating shaft 3 of the alternator 1, and can be rotated together with the rotating shaft 3. Hence, as shown in FIG. 11, a tapped hole 11 is formed in a middle portion of the inner peripheral surface of the sleeve 8, and the tapped hole 11 and an external thread formed on an external peripheral surface of a distal end portion of the rotating shaft 3 can be screwed with one another. A distal end portion of the inner peripheral surface of the sleeve 8 (the left end portion in FIG. 11) is provided with a locking hole 12 having a hexagonal section, so that a distal end of a tool, such as a hexagonal wrench, can be locked in the locking hole 12. A proximal end portion of the inner peripheral surface of the sleeve 8 (the right end portion in FIG. 11) is provided with a round hole 13 that fit, without a play, in a portion closer to the middle in the distal end portion of the rotating shaft 3.
To combine the sleeve 8 and the rotating shaft 3 so that they do not relatively rotate, other structure, such as a spline engagement structure, a noncircular fitting structure, or a key engagement may be employed. A central portion of the outer peripheral surface of the sleeve 8 has a large-diameter portion 14 that has a larger diameter than the rest thereof.
A half distal end portion of the outer peripheral surface of the driven pulley 7a is formed so that its section passing through an axis is serrated to hold a part of an endless belt called a poly-V belt. The roller clutch 10 is disposed at an axially middle portion in a space formed between the outer peripheral surface of the sleeve 8 and the inner peripheral surface of the driven pulley 7a, and the pair of bearings 9 are disposed at portions closer to both axial ends of the space so that the bearings axially clamp the roller clutch 10 from both ends.
The support bearings 9 support a radial load applied to the driven pulley 7a, while allowing relative rotation of the driven pulley 7a and the sleeve 8. The bearings 9 use, for example, deep-groove ball bearings.
The roller clutch 10 allows the transmission of torque between the driven pulley 7a and the sleeve 8 only if the driven pulley 7a attempts to relatively rotate in a predetermined direction with respect to the sleeve 8.
To construct the roller clutch 10 as described above, a clutch inner ring 21 is externally fitted and secured to the large-diameter portion 14 of the sleeve 8 by tightening. The clutch inner ring 21 is formed by subjecting a steel sheet made of cement steel or the like to plastic working, such as press working, to form the entire body into a cylindrical shape, a cam surface 22 being formed on its outer peripheral surface. More specifically, a plurality of recessed sections 23 like ramps are equidistantly formed in the circumferential direction in the outer peripheral surface of the clutch inner ring 21 thereby to form the cam surface 22. A chamfered portion 24 shaped like a conical recessed surface is formed on one end portion (the left end portion in FIG. 11) of the inner peripheral surface of the clutch inner ring 21. The chamfered portion 24 serves as a guiding surface for press-fitting the clutch inner ring 21 onto the outer peripheral surface of the large-diameter portion 14.
Furthermore, a clutch outer ring 25 is internally fitted and secured to a middle portion of the inner peripheral surface of the driven pulley 7a by tightening. In the inner peripheral surface of the clutch outer ring 25, at least an axially middle portion abutting against rollers 26, which will be discussed hereinafter, is shaped simply as a cylindrical surface. The clutch outer ring 25 is formed by subjecting a steel sheet made of cement steel or the like to plastic working, such as press working, to form the entire body into a cylindrical shape, and inward flange-shaped jaws 27a and 27b, which provide a circular portion, are formed on both axial ends thereof. Of the two jaws 27a and 27b, the jaw 27a has the same thickness as the cylindrical portion of the clutch outer ring 25 because it is formed beforehand in the manufacture of the clutch outer ring 25. On the other hand, the jaw 27b is made thinner because it is formed across the diameter inside the clutch outer ring 25 after the rollers 26, which will be discussed later, and a clutch retainer 28 are installed.
A plurality of rollers 26 constructing the roller clutch 10, together with the clutch inner ring 21 and the clutch outer ring 25, are supported by the clutch inner ring 21 by the externally fitted clutch retainer 28, which is prohibited from rotating in relation to the clutch inner ring 21, such that they are allowed to roll and to be slightly displaced in the circumferential direction. The clutch retainer 28 is formed of a synthetic resin (e.g. a mixture made by adding about 20% of glass fiber to a synthetic resin, such as polyamide 66, polyamide 46, or polyphenylene sulfide) into a cage-like cylindrical shape. Each segment of the clutch retainer 28 has a pair of annular rims 29 and a plurality of pillars 30 connecting the paired rims 29.
A square space surrounded by the inner side surfaces of the rims 29 and the circumferential side surfaces of the pillars 30 constitutes a pocket 31. Each of the rollers 26 is supported in each of the pockets 31 such that it rolls and is slightly displaced in the circumferential direction. Furthermore, an arc-shaped protuberances 32 are formed on a plurality of locations on the inner peripheral surface of each rim 29, and the clutch retainer 28 is loosely fitted to the clutch inner ring 21. The protuberances 32 are engaged with the recessed sections 23 formed in the outer peripheral surface of the clutch inner ring 21 so as to prohibit the relative rotation with respect to the clutch inner ring 21.
Furthermore, a leaf spring 33 is held by a retaining section 30a provided on a circumferential side surface of the pillar 30, and disposed in each of the pockets 31. The leaf spring 33 faces a portion, which becomes narrower across the diameter, of a cylindrical gap formed between the outer peripheral surface of the cam surface 22 and the inner peripheral surface (cylindrical surface) of the middle portion of the clutch outer ring 25, and elastically presses the roller 26 in the circumferential direction of the clutch retainer 28. Both axial end surfaces of the clutch retainer 28 closely oppose the inner side surfaces of the two jaws 27a and 27b of the clutch outer ring 25 so as to prevent axial displacement of the clutch retainer 28.
In the pulley device incorporating the one-way clutch constructed as described above, if the driven pulley 7a and the sleeve 8 attempt to relatively rotate in a predetermined direction, then the rollers 26 move into the portion, which becomes narrower across the diameter, of the cylindrical gap formed between the outer peripheral surface of the cam surface 22 and the inner peripheral surface (cylindrical surface) of the middle portion of the clutch outer ring 25 to lock the driven pulley 7a and the sleeve 8 so that they cannot relatively rotate. On the other hand, when the driven pulley 7a and the sleeve 8 relatively rotate in a direction opposite to the predetermined direction, the rollers 26 withdraw to a portion, which becomes wider across the diameter, of the cylindrical gap formed between the outer peripheral surface of the cam surface 22 and the inner peripheral surface of the middle portion of the clutch outer ring 25, allowing the driven pulley 7a and the sleeve 8 to perform relative rotation (overrun).
The following will describe advantages obtained by applying the pulley device with the built-in one-way clutch to an alternator.
If a drive engine is a diesel engine, fluctuations in the rotational angular velocity of a crankshaft increase during low-speed revolution, such as in an idling mode. As a result, the running speed of an endless belt installed on a drive pulley finely fluctuates accordingly. On the other hand, changes in the rotational speed of the rotating shaft 3 rotatably driven by the endless belt via a driven pulley are not very sudden because of inertial mass of the rotating shaft 3 and a rotor secured to the rotating shaft 3.
As a result, if the driven pulley is simply secured to the rotating shaft 3, then the endless belt and the driven pulley tend to rub each other in both directions as the rotational angular velocity of the crankshaft changes. This causes stress to be repeatedly applied in different directions to the driven pulley and the endless belt rubbing each other, leading to slippage taking place between the endless belt and the driven pulley or a shortened service life of the endless belt.
When the pulley device with the built-in one-way clutch is used as the driven pulley, if the running speed of the endless belt is fixed or increasing, then the torque is transmitted from the driven pulley 7a to the rotating shaft 3. Conversely, if the running speed of the endless belt is decreasing, then the driven pulley 7a and the rotating shaft 3 perform relative rotation. Hence, if the running speed of the endless belt is decreasing, then the rotational angular velocity of the driven pulley 7a is set to be lower than the rotational angular velocity of the rotating shaft 3 to prevent severe rubbing between the endless belt and a contacting portion of the driven pulley 7a. With this arrangement, the direction of the stress applied to the rubbing portions of the driven pulley 7a and the endless belt can be fixed, thereby preventing the slippage between the endless belt and the driven pulley 7a and also preventing the shortening of the service life of the endless belt.
Furthermore, if the driven pulley is just secured to the rotating shaft 3, and if the rotational speed of the drive engine suddenly drops, then the rotational speed of the rotor secured to the rotating shaft 3 accordingly drops, resulting in a sudden drop in the amount of power generated by the alternator. In contrast to this, when the pulley device incorporating the one-way clutch is used as the driven pulley, even if the rotational speed of the driven engine suddenly drops, the rotational speed of the rotor slowly drops due to an inertial force, allowing power generation to be continued during the slow drop in the rotational speed of the rotor. With this arrangement, kinetic energies of the rotating shaft and the rotor can be effectively utilized with a resultant increased power generated by the alternator, as compared with a case where a fixed driven pulley is used.
When this type of pulley device incorporating the one-way clutch is mounted on an alternator or a starter motor, if the rotational speed of an engine considerably fluctuates, then the clutch is constantly overrun, leading to constant slippage between the rollers and the outer ring with resultant generation of considerable amount of heat. Thus, the frictional heat heats the pulley device incorporating the one-way clutch to a high temperature. In the conventional pulley device incorporating the one-way clutch, the clutch retainer 28 is made of a synthetic resin, so that the frictional heat deteriorates the rigidity of the clutch retainer 28. This has been presenting a problem in that the clutch retainer 28 may deform and interfere with an operation of the clutch or the clutch retainer 28 may incur thermal deterioration, failing to provide stable operation or satisfactory durability.
There has also been a problem in that the clutch retainer 28 has a complicated cage-like cylindrical shape, so that the productivity is poor, preventing a reduction in cost.
There has been another problem in that, since the clutch retainer 28 and the leaf spring 33 are made as separate components, meaning more components, and careless skipping of the installation of the leaf spring 33 tends to happen with resultant poor assembly efficiency.
There has been yet another problem in that the clutch retainer 28 is axially positioned by being held between the two jaws 17a and 17b of the clutch outer ring 25, so that the clutch retainer 28 is required to have highly accurate dimensions, leading to poor productivity.
The present invention has been made with a view toward solving the problems described above, and it is an object of the present invention to provide a rotation transmitting device incorporating a one-way clutch that has a metallic clutch retainer to improve its resistance to heat so as to provide high durability and stable operation.
In order to achieve the above object, according to one aspect of the present invention, there is provided a rotation transmitting device incorporating a one-way clutch, including: an inner member secured to an end of a rotating shaft; a cylindrical outer member disposed around the inner member so that it is concentric with the inner member; a one-way clutch that is provided between an axially middle portion of an outer peripheral surface of the inner member and an axially middle portion of an inner peripheral surface of the outer member, and allows torque to be transmitted between the outer member and the inner member only if the outer member attempts to perform relative rotation in a predetermined direction in relation to the inner member; and a pair of support bearings that are provided between the outer peripheral surface of the inner member and the inner peripheral surface of the outer member so as to hold the one-way clutch from both axial ends, and allow the inner member and the outer member to relatively rotate while supporting a radial load applied to the outer member, wherein the one-way clutch has a cylindrical clutch outer ring fixedly fitted externally to an axially middle portion of the inner peripheral surface of the outer member, a cylindrical clutch inner ring that is fixedly fitted externally to an axially middle portion of the outer peripheral surface of the inner member and that has its outer peripheral surface formed to be a cam surface with wedge-shaped spaces provided at predetermined pitches in a circumferential direction, the wedge-shaped spaces being defined by gaps that are formed between the outer peripheral surface thereof and the inner peripheral surface of the clutch outer ring and that gradually become narrower in one circumferential direction, rollers disposed in the respective wedge-shaped spaces, spring members disposed in the wedge-shaped spaces such that they urge the rollers toward portions with smaller radial widths of the wedge-shaped spaces, and a clutch retainer that is disposed such that it cannot perform relative rotation with respect to the clutch inner ring and supports the rollers such that the rollers may roll and be displaced in a circumferential direction, and wherein the clutch retainer is made of metal.
According to another aspect of the present invention, there is provided a rotation transmitting device incorporating a one-way clutch, including: an inner member secured to an end of a rotating shaft; a cylindrical outer member disposed around the inner member so that it is concentric with the inner member; a one-way clutch that is provided between an axially middle portion of an outer peripheral surface of the inner member and an axially middle portion of an inner peripheral surface of the outer member, and allows torque to be transmitted between the outer member and the inner member only if the outer member attempts to perform relative rotation in a predetermined direction in relation to the inner member; and a pair of support bearings that are provided between the outer peripheral surface of the inner member and the inner peripheral surface of the outer member so as to hold the one-way clutch from both axial ends, and allow the inner member and the outer member to relatively rotate while supporting a radial load applied to the outer member, wherein the one-way clutch has a cylindrical clutch outer ring fixedly fitted internally to an axially middle portion of the inner peripheral surface of the outer member, a large-diameter portion of the inner member that is formed on an axially middle portion of the outer peripheral surface of the inner member and that has its outer peripheral surface formed to be a cam surface with wedge-shaped spaces provided at predetermined pitches in a circumferential direction, the wedge-shaped spaces being defined by gaps that are formed between the outer peripheral surface thereof and the inner peripheral surface of the clutch outer ring and that gradually become narrower in one circumferential direction, rollers disposed in the respective wedge-shaped spaces, spring members disposed in the wedge-shaped spaces such that they urge the rollers toward portions with smaller radial widths of the wedge-shaped spaces, and a clutch retainer that is disposed such that it cannot perform relative rotation with respect to the inner member and supports the rollers such that the rollers may roll and be displaced in a circumferential direction, and wherein the clutch retainer is made of metal.